The present invention relates to a method and to a system for extracting one or more of starch, protein and oil from grains that include a germ.
Grain milling, such as corn milling, has been performed in the United States since about 1842. Two types of grain milling have been developed, wet milling and dry milling. As suggested by the name, wet milling employs water during grinding and in dry milling, grain such as corn, is ground without water.
Over the years, wet grain milling processes have gone from batch processes to continuous processes. One prior art wet milling process is illustrated at 1 in FIG. 2. The wet milling processes have improved in efficiency by re-using aqueous process streams, and by performing counter-current operations, in order to recover corn constituents. Specifically, in wet milling, a soluble protein component of grain is steeped, as shown at 2, in FIG. 2, extracted, and washed before grinding, as shown at 3. Components of grain, such as germ fiber and gluten are extracted, as shown at 4 and 5 before starch is finally washed, as shown at 6 in FIG. 2.
Dry milling of corn has been used to produce similar products to wet milling, such as corn germ and corn grits but without the efficiencies of wet milling that reclaims a high purity starch as a final product. One prior art dry milling process is shown at 100 in FIG. 3.